The present invention generally relates to gaskets for use in an internal combustion engine and a method for fabricating the same. More particularly, the present invention is directed to a multi-layer gasket for use in motorcycle engines.
Head gaskets currently used in internal combustion engines, and in particular in engines for Harley Davidson motorcycle engines, are typically comprised of graphite with an aluminum liner around an inner circumference of the gasket and a polyethylene bead patterned on the aluminum liner which functions to enhance the seal of the gasket. However, the polyethylene bead has proven to actually inhibit a good seal because the graphite material which comprises the gasket cannot adequately bend around the polyethylene bead to form a tight seal.
Copper is more heat resistant than aluminum while still being formable and pliable to form a tight seal. Accordingly, many prior art gaskets have incorporated the use of a copper layer to aid in forming an effective seal such as those described in U.S. Pat. Nos. 4,836,158, 4,973,516, and 5,100,737. Still, adhesives are used with many gaskets having copper layers in order to create strong and effective seals.
Like the head gaskets described above, lower rocker box gaskets used in Harley Davidson motorcycle engines are also typically comprised of graphite. Lower rocker box gaskets also typically include tabs which extend from an inner aperture located in the center of the gasket which are folded onto the engine in order to position and help seal the gasket. The tabs function to assist sealing of the gasket without the use of an adhesive. The use of such tabs, as well as the use of adhesives and head gaskets requires more tooling and/or more steps in the manufacture of the gaskets and their application as used in internal combustion engines.
Accordingly, there is a need for an improved gasket which does not require the use of adhesives or tabs to create a tight and effective seal in internal combustion engines.
The present invention is directed to an improved gasket for internal combustion engines which decreases tooling and/or manufacturing costs and improves performance.
The gasket of the present invention includes a copper base layer, a graphite layer overlying the copper base layer, an aluminum layer overlying the graphite layer, and a second graphite layer overlying the aluminum layer. In one aspect of the invention, the copper base layer is folded over an interior circumference of the gasket and onto the second graphite layer in order to form a copper lip over the internal circumference of the gasket.
In another aspect of the invention, a top copper layer is positioned over the second graphite layer and in still another aspect of the invention the bottom copper layer is folded over an inner circumference of the gasket and onto the top copper layer in order to form a copper lip over the internal circumference of the gasket.
In another embodiment of the invention, a lower rocker box gasket for a motorcycle engine is formed from any of the present invention gaskets previously described above but without any center tabs extending from an aperture contained in the gasket. These embodiments and aspects of the present invention result in a gasket having an improved seal without the need for tooling to create tabs and adhesive layers and/or beads in the gasket.
These and other objects and advantages of the invention, as well as the details of illustrative embodiments, will be more fully understood from the following specification and drawings.